Durability Of High Strength Concrete Research Articles

The effects of steel, polypropylene, and high-performance macro polypropylene fibers on mechanical properties and durability of high-strength concrete

Present study aimed to compare the properties of high-strength and ordinary concrete containing polypropylene fibers (PPFs), high-performance synthetic macro polypropylene (HPP) fibers, and steel fibers (SF) under standard and sulfate curing conditions. The high-strength concrete with water-to-cement ratios of 0.38, 0.33, and 0.28 were tested. The addition of PPF and SF reduced the workability of these mixtures containing supplementary cementitious material. The highest compressive strength belongs to the mixture containing 1% of SF and 0.2% of PPF. The highest tensile strength belongs to the mixture containing 0.5% of HPP fibers with 1% of SF and 0.2% of PPF. The highest flexural strength of the mixture containing 0.5% of HPP fibers with 1% of SF. Fiber- reinforced concretes have less 30-minute water absorption than non-fiber samples. The minimum absorption belongs to the sample containing 0.5% of PPF with 20% of silica fume in the amount of 0.53%.

Long-term mechanical properties and durability of high-strength concrete containing high-volume local fly ash as a partial cement substitution

High-volume fly ash (HVFA) is a commonly used partial substitution for cement in mortar and concrete production. The present study was developed to examine the potential of using local HVFA as a partial substitution for cement in high-strength concrete (HSC). The effects of FA inclusion on the long-term mechanical properties and durability of concrete were investigated. The HSC samples were prepared with different FA substitution ratios, ranging from 0% to 50% by weight (ratio between FA to total weight of cement and FA) at 10% interval. Long-term properties were evaluated through compressive strength (CS) and ultrasonic pulse velocity (UPV) tests, while durability was examined through water absorption (WA), drying shrinkage (DS), and rapid chloride ion penetration (RCPT) tests. The results indicate that, at 28 and 56 days, higher FA content was associated with lower HSC performance. However, at 120 days, the 30% FA sample achieved the highest performance of all of the samples in terms of long-term mechanical properties and durability. Moreover, higher FA content was associated with less DS. Also, no significant change in the water absorptivity value of the HSC samples was observed. All of the HSC samples at 28, 56, and 120 days of curing age had UPV values of above 4100 m/s, indicating “very good quality” concrete. In addition, all of the HSC samples exhibited “very low” chloride permeability. Finally, the results of the environmental analysis found that incorporating a high volume of locally sourced FA as a partial substitution for cement in HSC reduced both CO2 emissions (CO2-E) and energy consumption (EC), which may help further promote the sustainability of the construction industry.

Residual Mechanical Properties and Durability of High-Strength Concrete with Polypropylene Fibers in High Temperatures.

Investigations into the fire resistance of high-strength concrete (HSC) is extremely important to optimize structural design in construction engineering. This work describes the influence of polypropylene fibers on the mechanical properties and durability of HSC at high temperatures (25, 100, 200, 400, 600 and 800 °C). HSC specimens with 2 kg/m3 composed of polypropylene fibers are tested in a temperature range of 25 to 800 °C, followed by microstructural analysis. In addition, a statistical analysis is designed to identify the effect of factors, namely temperature and polypropylene fibers, and their interactions on mechanical properties and water absorption, electrical resistivity, mass loss and ultrasonic velocity. Most of the properties are improved by the incorporation of fibers, obtaining highly predictable regression models. However, the polypropylene fibers reduce compressive strength but improve the residual mechanical properties up to 400 °C.

High strength concrete using ground granulated blast-furnace slag with Alccofine and with silica fume

High strength concrete (HSC) is highly promising building material widely used in large scale concrete constructions that require high strength, high flow ability and high durability. Several studies have been carried out in past decades to identify the use of supplementary cementitious material in concrete. To increase the durability along with strength of concrete leads to the use of high-strength concrete which is more beneficial for environmental attacks on the structure. Various studies are performed on HSC with respect to workability, strength and durability. The addition of different mineral and chemical admixtures increases the strength and durability of HSC. The effect of SCM on strength and durability of High Strength Concrete (HPC) using ground granulated blast-furnace slag (GGBS) with Alccofine and GGBS with silica fume is studied.

Durability Studies on High Strength Concrete

High strength concrete (HSC) is very useful for recent construction technology; the major problem of HSC is the insufficient ductility. To investigate the ductility of HSC, the entire stress-strain curve, especially in the descending branch, shall be recorded. The aim of this study is to investigate the durability of High strength concrete for different replacement levels of mineral admixtures by alternate wetting and drying phenomenon which includes; acid attack, sulphate resistance and marine Environment and also to determine the compressive strength of concrete as GGBFS partial replacement for cement. Concrete mix is designed for M80 Grade of concrete using modified ACI method. Maximum Compressive Strength of 96.4MPa and 91.6 MPa at 28days were found for the HSC specimens at a partial replacement of cement with 30% of GGBFS in normal water curing and accelerated curing tank respectively. The specimens immersed in marine solution were found to have less weight loss when compared to acids and sulphate solution.

Durability and Compression Properties of High-Strength Concrete Reinforced with Steel Fibre and Multi-walled Carbon Nanotube

High-strength concrete (HSC) reinforced with steel fibre (SF) and carbon nanotube (HSCRSC) is a new type of high-strength composite concrete with good fluidity, high strength, toughness, durability and other remarkable advantages. HSCRSC can be widely used in underground structures, such as wellbores. In this study, HSCs ranging from 70 to 100 MPa were designed, and the effects of fibre on the performance of the HSCs were compared and analysed through single-doped and double-mixed SF and multi-walled carbon nanotubes. Results showed that the fibre effectively improved the uniaxial and multiaxial compressive strengths and durability of HSCs and changed the failure mode from brittle to ductile, especially in the case of multiaxial compression failure. HSCs remained intact, but the plain concrete specimens had fractured forms, such as flakes, columns and layers. Moreover, the ultimate strength of the biaxial compression was between 1.10 and 1.39 times higher than that of the uniaxial compression, satisfying the Kufer–Gerstle criterion. The ultimate strength of the triaxial compression was between 1.24 and 2.55 times higher than that of the uniaxial compression, adhering to the Willam–Warnke meridian criterion. The modified B3 model met the prediction accuracy of shrinkage and creep for HSC and surpassed the biaxial and triaxial compression ultimate strength models provided in this study. The absolute value of the relative error was less than 6%, indicating that the model and test data were reliable. All test results showed that HSCRSC exhibited satisfactory comprehensive performance.

Evaluating Strength Development and Durability of High-Strength Concrete with 60% of Ground-Granulated Blast Furnace Slag

This experimental study investigates material properties and durability of high-strength concrete (HSC) using ground-granulated blast-furnace slag (BS) and hooked steel fiber. The test results indicated that the compressive and flexural strengths of the BS-blended concretes are higher than those of ordinary Portland cement up to 28-day aging after steam curing. The porosity decreased with the usage of the BS, and thus, the matrix became dense. Therefore, the BS-blended HSC is highly impermeable to water, regardless of whether it undergoes cracking, and some negative effects on the resistance against freezing and thawing actions. In addition, it has low resistance to carbonation despite low amounts of calcium hydroxide. However, it was confirmed that used as structural materials can be resistant to carbonation in long-term durability. Keywords: High-strength Concrete, Ground Granulated Blast Furnace Slag (BS), Strength Characteristic, Water Permeability, Durability

Mechanical properties and durability of high-strength concrete containing macro-polymeric and polypropylene fibers with nano-silica and silica fume

The current study investigates the effects of different amounts of polypropylene (PP) and macro-polymeric (MP) fibers on the mechanical properties and durability of high-strength concrete containing silica fume and nano-silica. In total, 280 concrete specimens were produced in 28 different test groups, for which the parameters of compressive strength, tensile strength, modulus of elasticity, water absorption, and porosity were evaluated. The macro-polymeric fibers in volume fractions of 0.25, 0.5, 0.75, 1.0, and 1.25%, and the polypropylene fibers in volume fractions of 0.1, 0.2, 0.3, 0.4, and 0.5% were used in this study. Furthermore, one set of specimens with the total fiber volume fraction of 1.0% of the concrete volume was tested in order to examine the effect of hybrid polypropylene-macro-polymeric fibers on the concrete properties. In addition, the nano-silica with the weight percentages of 1, 2, and 3%, and the silica fume with the weight percentages of 8, 10, and 12% were employed in the concrete mix design. In the current paper, first, the effects of macro-polymeric, polypropylene, and hybrid fibers on the physico-mechanical properties were comparatively examined, and then the influence of using nano-silica and silica fume in the high-strength concrete with no included fiber was investigated. Finally, the optimum percentages of fibers and pozzolans corresponding to the most significant increases in the tensile strength were chosen, which were subsequently used as the optimum combination of the high-strength concrete. The results of the experimental study suggest an improvement in the concrete mechanical properties and durability following the introduction of nano-silica and silica fume. In addition, incorporating macro-polymeric fibers in the concrete mixture given the volume content of fibers improves the mechanical properties of high-strength concrete. Moreover, high volume fractions of polypropylene fibers in the concrete mixture brought about negative effects on the physico-mechanical properties of the high-strength concrete.

석회암 굵은골재를 사용한 고강도 콘크리트의 역학 및 내구특성

In this research, engineering performance and durability of high strength concrete using limestone coarse aggregate were evaluated to suggest applying the waste limestone aggregate on high strength concrete through the treating processes of crushing and size distribution. As the results of a series of tests, about 5 % of workability was improved with limestone coarse aggregate while there is no significant difference on air content. As a hardened concrete properties, early age compressive strength was increased and elastic modulus was improved about 12 % when limestone coarse aggregate was used in high strength concrete. In autogenous shrinkage, the deformation amount was significantly decreased. For durability of high strength concrete using limestone coarse aggregate, generally favorable results were obtained due to the low water-to-binder ratio in freeze-thawing, carbonation, sulfate attack, and chloride penetration. From the spalling resistivity test simulating fire condition, favorable results were obtained regardless types of aggregate depending on the fiber content. Consequently, it was possible to achieve equivalent or better performance of high strength concrete using the limestone coarse aggregate.

Rheological Property and Durability of High Strength Concrete Using Zeolite Powder and Microsphere

The rheological property of fresh high-strength concrete (HSC) and mechanical properties, self-shrinkage and resistance to chloride ion permeability of hydrated HSC were studied on the basis of the closest packing theory. Results showed that the packing density of composite powder was the highest when the content of microsphere was 30.0%; when the content of zeolite powder added to concrete varied from 0.0% to 4.0%, the rheological and discontinuous property of concrete would be improved and its viscosity would be increased; meanwhile, compared to the standard concrete, the self-shrinkage of concrete with 2.0% zeolite powder at 1d, 3d, 7d and 28d was decreased by 77.1%, 49.6%, 44.0% and 38.1% respectively; finally, the resistance to chloride ion permeability of hydrated HSC with zeolite powder was improved with a result of 18.5% reduction of electric flux at 28d.

Shrinkage-Reducing Admixture: Effects on Durability of High-Strength Concrete

Shrinkage-reducing admixture (SRA) is a mitigation strategy against autogenous shrinkage in high-strength concrete (HSC). It acts by reducing the surface tension of the fluid in the pore system of the cement paste. An experimental program was carried out to investigate the influence of SRA on concrete durability, as few studies about this subject have been developed. Its effectiveness in reducing autogenous shrinkage and its influence on compressive strength were also evaluated. The results showed a substantial reduction of autogenous shrinkage due to the presence of the SRA, with a slight reduction on compressive strength (up to 5%). Overall, concrete durability under the action of aggressive agents (such as water, CO2, and chloride ingress) was not influenced by SRA, as verified in the results of chloride penetration, natural carbonation, water permeability, capillary absorption of water, and absorption of water tests.

高強度コンクリートの耐久性と構造物の高耐久化

高強度コンクリートの耐久性と構造物の高耐久化

Performance of high strength concrete made with copper slag as a fine aggregate

This research study was conducted to investigate the performance of high strength concrete (HSC) made with copper slag as a fine aggregate at constant workability and to study the effect of superplasticizer addition on the properties of HSC made with copper slag. Two series of concrete mixtures were prepared with different proportions of copper slag. The first series consisted of six concrete mixtures prepared with different proportions of copper slag at constant workability. The water content was adjusted in each mixture in order to achieve the same workability as that for the control mixture. Twelve concrete mixtures were prepared in the second series. Only the first mixture was prepared using superplasticizer whereas the other eleven mixtures were prepared without using superplasticizer and with different proportions of copper slag used as sand replacement. The results indicated that the water demand reduced by almost 22% at 100% copper slag replacement compared to the control mixture. The strength and durability of HSC were generally improved with the increase of copper slag content in the concrete mixture. However, the strength and durability characteristics of HSC were adversely affected by the absence of the superplasticizer from the concrete paste despite the improvement in the concrete strength with the increase of copper content. All concrete mixtures did not meet the strength and durability design requirements due to the segregation and dryness of the concrete paste. Therefore it can be concluded that the use of copper slag as sand substitution improves HSC strength and durability characteristics at same workability while superplasticizer is very important ingredient in HSC made with copper slag in order to provide good workability and better consistency for the concrete matrix.

Effects of Fly Ash and Ground Granulated Blast-Furnaces Slag on Properties of High-Strength Concrete

Effects of fly ash and ground granulated blast-furnace slag (GGBFS) on workability, strength, volume stability and durability of HSC are investigated. Results show that fly ash and GGBFS can improve the workability, increase the later strength of high strength concrete (HSC) remarkably, and reduce the brittleness. In addition, the ameliorative effect of GGBFS on HSC brittleness is more remarkable. With the increase of fly ash and GGBFS, the early elastic modulus of HSC reduces. The elastic modulus is similar to the controlled sample when the load is applied after 60d curing. The fly ash and GGBFS can improve HSC’s resistance to chloride ion penetration significantly. However, the effects of fly ash and GGBFS on freezing-hawing resistance of HSC are not obvious. Besides, the fly ash will reduce freezing-hawing resistance of HSC only when the content of mineral powder is up to 36%.

LONG -TERM BEHAVIOR OF SILICA FUME CONCRETE EXPOSED TO DIFFERENT AGGRESSIVE MEDIA

The durability of high strength concrete (HSC) was experimentally investigated in terms of compressive, tensile and bond strengths. The effect of curing media, (air and tap water) and the effect of emersion in sea- water were taken into consideration. The silica fume (SF) concrete specimens were exposed directly to two types of environmental attack (sodium sulphate and sodium chloride). The specimens were submerged in two different solutions of sodium sulphate having concentrations of 5% and 7% and sodium chloride of 2% and 4% concentrations. The specimens were tested after 28, 360, 540 and 720 days. The SF addition was 10% by weight of cement. Test results showed that the compressive, tensile and bond strengths generally increase, with higher early age strength and higher early rate of strength gain, with time up to about two years. High strength concrete, incorporating silica fume, when exposed to sulphate and chloride solutions, exhibits highest values, higher rates of increase and the lowest rates of decrease of compressive strength up to 24 months. X-ray diffraction (XRD) patterns of the hardened specimens were plotted for all cured conditions, which explain the chemical compounds formed aRer hardening.

Bestimmung der Dauerhaftigkeit von Hochleistungsbeton mit Hilfe des CDF-Tests / Determination of the durability of high performance concrete by means of CDF-test

Abstract Variable obsen>ations concerning frost resistance of high performance concrete have been made. The question arises which are the decisive factors influencing durability under the action of frost and de-icing salt. The proposed experiments are to be carried out in cooperation with F.A.- Finger - Institute of Bauhaus University Weimar. The aim of this study is to determine possible change of durability of high strength concrete, and to investigate the origin thereof. Measures to reduce the risk of reduced durability have to be found.

Effect of Microcracking on Durability of High-Strength Concrete

The relationship between cracking and chloride and water permeability of high-strength concrete (HSC) was studied. Two different mix designs were used: HSC_1 (w/b = 0.31) and HSC_2 (w/b = 0.25). The effects of crack width and sample thickness on permeability were examined. Cracks of designed widths were induced in the concrete specimens using the feedback-controlled splitting tensile test. Chloride permeability of the cracked samples was evaluated by using a rapid chloride permeability test. The water permeability of cracked concrete was then evaluated by a low-pressure water permeability test. Among the materials tested, only high-strength concrete with a very low water-to-cement ratio conductivity is sensitive with respect to cracking. The water permeability of cracked HSC significantly increases with increasing crack width. Among the parameters considered, crack parameters significantly affect water permeability, and there is little thickness effect. The results indicate that the water permeability is significantly more sensitive than conductivity with respect to the crack width used.

Creep, shrinkage, frost, and sulphate resistance of high strength concrete

A comprehensive study was undertaken to determine the shrinkage, creep, and durability of high strength concrete (50–70 MPa) containing silica fume and lignite fly ash. The concrete mixtures contained normal CSA type 10 (ASTM type 1) portland cement, 10% condensed silica fume, and different amounts of fly ash that varied between 0 and 80% of the weight of binder in the mixture. The aggregates-to-binder ratio by weight was maintained at 5 and the weight of the superplasticizer was varied between 1.5% and 2.2% of the binder while the water-to-binder ratio was maintained at 0.27. The test program consisted of compressive strength tests at various ages on concrete cylinders; drying shrinkage tests at room temperature; creep tests of sealed and unsealed concrete at room temperature (21 °C (70°F)) and at high temperatures (up to 232 °C (450°F)) under three different stress regimes; frost resistance tests on concrete prisms up to 300 freezing and thawing cycles; and sulphate resistance tests on concrete prisms immersed in 5% Na2SO4 solution for up to 10 months. The results indicated that up to 60% fly ash replacement with 10% silica fume showed either superior or similar 28- and 56-day compressive strengths when compared with the 100% cement control mixture. Fly ash + silica fume concrete indicated lower shrinkage and long-term creep. Creep increased with increase in temperature due to physico-chemical processes, which were confirmed by microstructure analysis using the scanning electron microscope. The creep and shrinkage data of high fly ash + silica fume concrete fitted well to the current ACI creep and shrinkage model. Replacement of cement by up to 35% fly ash and 10% silica fume indicated enhanced frost resistance, without any air-entrainment. The addition of 8% air-entrainment to the 20% fly ash + 10% silica fume mixture increased the durability factor by about 10%. For the 50% fly ash + 10% silica fume mixture, the frost durability factor was found comparable to that of the 100% cement control mixture, and air entrainment did not improve its value appreciably. Sulphate resistance of concrete made with 100% CSA type 10 cement was found satisfactory; however, with increasing fly ash contents (up to 50%), the expansion due to sulphate action was suppressed. A study of matrix morphology and microstructure bonding, using the scanning electron microscope, helped to explain the observed results in a comprehensive manner. Key words: creep, shrinkage, compressive strength, frost resistance, durability factor, sulphate resistance, fly ash, silica fume, high-strength concrete, SEM micrograph, matrix morphology.